It is known that biological samples are treated in different ways in order to obtain the isolation of particular types of particles (normally, cells).
Examples in this regard are the devices and methods described in the patent applications PCT/IB2010/000615 PCT/IB2010/000580 (relative to the DEPArray™ system).
Usually, at the end of the above-mentioned treatments, samples are obtained in which the particles are inserted at low concentrations in a liquid component. In this regard, it should be noted that the liquid component is normally a buffer, which cannot be used in subsequent analysis steps, and the volume of the samples is usually too high. For example, the samples obtained following use of the DEPArray™ system have volumes of approximately 38 μL, whereas subsequent steps (like WGA—Whole Genome Amplification) require volumes lower than 1 μL.
The samples therefore have to be treated by centrifugation at high speed and an operator has to very carefully withdraw the excess liquid manually using a pipette (and slanting the test tube containing the sample). There are many problems connected with this procedure, including:                the success of the operations depends largely on the ability of the operator; there is a risk, which can be high if the operator does not operate correctly, of removing the particle together with the excess liquid. The success rate of the procedure is not reliable and cannot always be reproduced, and depends on the type of buffer used;        the operations are relatively slow;        the procedure requires particular care, such as the use of dedicated pipettes and contamination-free tips with dual filter to reduce the risk of the sample becoming contaminated during handling by the operator;        there is a relatively high risk of the particle/s being damaged due to the centrifugation which, as mentioned, is performed at relatively high speeds (therefore imparting a relatively high stress to the particle/s).        
The object of the present invention is to provide a hollow device, a covering device, an apparatus, a kit and a method which overcome, at least partially, the drawbacks of the known art and if possible are, at the same time, easy and inexpensive to produce.